The present invention generally relates to fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly relates to a forced draft, fuel-fired furnace having incorporated therein specially designed apparatus for utilizing combustion air to cool its draft inducer fan motor.
Various types and sizes of fuel-fired heating appliances are provided with draft inducer fans which are communicated with the interior of the heat exchange portion of the appliance and serve to forcibly expel combustion gases therefrom and deliver the expelled combustion gases to a vent stack structure operatively coupled to the appliance. For example, in conventional forced draft, fuel-fired air heating furnaces the draft inducer fan is often located within a burner vestibule area of the furnace, with a negative pressure created in the vestibule area by the draft inducer fan being utilized to draw combustion air into the vestibule, via louvers or other openings in an exterior wall portion of the vestibule, for delivery to the burners in the vestibule. Combustion air entering the vestibule flows freely through the substantially open interior of the vestibule to the burners.
Because the draft inducer fan is located in the enclosed furnace vestibule area of the furnace, the inducer fan motor can often be subjected to undesirably high operating temperatures. One previously proposed solution to this potential inducer fan motor overheating problem is illustrated and described in U.S. Pat. No. 6,382,203 to Kim et al and comprises the provision of an air transfer duct structure extending through the interior of the vestibule chamber and mechanically interconnected between the air intake opening and the draft inducer fan motor. Operation of the draft inducer fan cools its motor by flowing substantially all of the combustion air entering the air intake opening through the transfer duct structure and across the inducer fan motor prior to this incoming combustion air being discharged from the transfer duct structure and being delivered to the furnace burners within the vestibule chamber.
While this previously proposed combustion air-based inducer fan motor cooling technique provides for substantially enhanced cooling of the motor compared to the conventional approach of simply permitting the incoming air to migrate unchanneled through the substantially open vestibule chamber interior to the burners therein, it undesirably increases both the fabrication complexity and overall production cost of the furnace in which it is incorporated. A need thus exists for improved combustion air-based apparatus and methods for cooling the motor of a draft inducer fan disposed in a chamber portion of a furnace or other type of fuel-fired, forced draft heating appliance. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a fuel-fired, forced draft heating appliance, representatively a gas-fired air heating furnace, is provided and has a chamber having an exterior wall with an air intake opening therein, a heat exchanger, and a fuel burner representatively disposed in the chamber and operative to create hot combustion products in the heat exchanger.
A draft inducer fan is also disposed in the chamber and is operative to expel flue gas from the heat exchanger. During operation of the furnace, the draft inducer fan creates within the chamber a negative pressure that draws a first quantity of combustion air into the chamber, for delivery to the fuel burner, sequentially through the air intake opening, through the interior of the chamber via a substantially unenclosed flow path therein, and against the motor in a manner cooling it prior to delivery of the first quantity of combustion air to the fuel burner.
According to a key aspect of the present invention, this combustion air cooling of the draft inducer fan motor is enhanced by a deflector structure supported within the chamber in an inwardly spaced apart, facing relationship with the air intake opening. The deflector structure, which is representatively a flat deflector plate member supported in the chamber by an integral flat support portion, angled relative to the deflector plate, is operative to be impinged by the first quantity of combustion air after it enters the chamber and redirect such combustion air generally toward the draft inducer fan motor through the aforementioned substantially unenclosed flow path within the chamber. Representatively, operation of the draft inducer fan also draws a second quantity of combustion air, which may also impinge upon the deflector plate, inwardly through the air intake opening for delivery to the fuel burner through the interior of the chamber via a substantially unenclosed flow path therein which bypasses the draft inducer fan motor.
In a preferred embodiment of the furnace the fuel burner is representatively an inshot-type fuel burner and the furnace includes a baffle structure for shielding the burner from flicker-creating impingement by the combustion air being delivered to the burner; the draft inducer fan motor has a housing portion with a plurality of cooling openings therein via which a portion of the first combustion air quantity is drawn through the interior of the motor housing portion during operation of the draft inducer fan; and the draft inducer fan includes a fan housing, the fan motor is disposed externally of the fan housing and rotationally drives a shaft, and the draft inducer fan further includes a fan blade structure mounted on the shaft and operative to flow combustion air through the interior of the motor to enhance combustion air cooling of the motor.
While principles of the present invention are representatively illustrated and described herein as being incorporated in a fuel-fired, force draft air heating furnace, it will be readily appreciated by those of ordinary skill in this particular art that such principles could also be advantageously utilized in a variety of other types of fuel-fired, forced draft heating appliances as well, and are not limited to being applied to furnaces.